Most of the used recent electric vehicles, either road vehicles or naval vehicles or vehicles in public transport networks, include an electrical power distribution network also called DC bus on which is connected a drive and energy recovery system configured to operate in a given operating voltage range, and a storage system.
The present invention focuses on vehicles whose storage system comprises capacitive storage elements likely to be charged by a charging voltage delivered by the electrical power distribution network and comprised in the range of operation of the drive and energy recovery system.
The drive and energy recovery system generally comprises a reversible electric machine enabling an operation according to a mode called <<motor>> so as to ensure the driving or the traction/propulsion of the vehicle using a supplied electrical energy and enabling alternately an operation according to a mode called <<generator>> so as to ensure the conversion of the mechanical energy due to the braking or to the deceleration of the vehicle into electrical energy.
In the motor mode, the motor consumes electrical energy supplied thereto by the capacitive storage elements of the storage system.
In the generator mode, the motor produces electrical energy and charges the capacitive storage elements of the storage system.
The thermal/electric hybrid vehicles further comprise a thermal motor that can ensure by itself the driving of the vehicle but may also drive the reversible electric machine so as to make it operate in the generator mode.
Electrical energy supplied by the motor in the generator mode is then transmitted to the electrical power distribution network of the vehicle and recovered by the capacitive elements of the storage system in the same manner as during a braking or a deceleration of the vehicle.
In a known manner, the capacitive storage elements comprise in particular an assembly of double layer capacitances, also called supercapacitances, supercapacitors or EDLC (Electrolytic Double Layer Capacitor) in which electrical energy is stored.
This electrical energy stored in the capacitive storage elements may then be used as main or auxiliary energy for supplying the electric motor of the electric vehicle.
Furthermore, it is known to have a storage system comprising a DC-DC converter connected to the electrical power network of the vehicle and a drive and energy recovery system comprising a means for converting the current also connected to the electrical power network of the vehicle.
The DC-DC converter enables adapting the variable voltage of the capacitive storage elements of the storage system to the operating DC voltage of the drive and energy recovery system of the vehicle.
Furthermore, the DC-DC converter must be able, on the one hand to transfer in the motor mode the traction/propulsion total power from the capacitive storage elements of the storage system to the reversible electric machine via the electrical power network of the vehicle, and on the other hand to transfer in the generator mode the total braking power from the reversible electric machine to the capacitive storage elements of the storage system via the electrical power network of the vehicle.
As for the current converter, it allows to make the power supplied to the reversible electric machine in the motor mode vary depending on a control caused by a user for example by means of the accelerator pedal of the vehicle or any other controller.
The current converter must also be able to transfer the electrical energy coming from the reversible electric machine when it operates in the generator mode to the capacitive storage elements of the storage system via the DC-DC converter.
In a known manner per se, the current converter may either be a speed variator or an inverter.
A storage system connected to such drive and energy recovery system via the power distribution network of the vehicle is satisfactory in that it can be easily adapted to an existing traction/propulsion chain and enables decoupling the traction/propulsion and the storage functions.
These two functions are generally processed by two different sectors within a same company and the integration of a storage system and a drive and energy recovery system on the same electrical power distribution network of a vehicle does not require the intervention of the skilled in the art having carried out the traction/propulsion function of the vehicle.
However, a coupling between such storage system and such drive and energy recovery system has the drawback of accumulating the efficiencies of two converters, the one of the DC-DC converter and the one of the current converter which also comprises a static converter.
This cumulation of efficiencies decreases strongly the energy efficiency of the coupling between a storage system and a drive and energy recovery system due to cumulative conversion losses.
Moreover, such storage system also has the drawback of having to use a DC-DC converter having a significant overall dimension and mass.